What is the pressure gradient between the alveoli and intrapleural space referred to as?

• A. Transpulmonary pressure
• B. Intrapleural pressure
• C. Alveolar pressure
• D. Intrathoracic pressure

Answer: (A)

The pressure gradient between the alveoli and the intrapleural space is referred to as transpulmonary pressure. This pressure gradient is crucial for maintaining lung inflation and is defined as the difference between the alveolar pressure (the pressure inside the lung alveoli) and the intrapleural pressure (the pressure within the pleural cavity surrounding the lungs).

Transpulmonary pressure plays a vital role in keeping the lungs expanded. When alveolar pressure is greater than intrapleural pressure, it creates a pressure differential that allows the lungs to remain inflated during the respiratory cycle. This relationship is essential for normal ventilation and preventing lung collapse, known as atelectasis.

Intrapleural pressure refers specifically to the pressure within the pleural cavity, while alveolar pressure is the pressure in the alveoli. Intrathoracic pressure is a broader term that can refer to the pressure within the thoracic cavity as a whole, which includes but is not limited to intrapleural and alveolar pressures. Thus, transpulmonary pressure specifically describes the important gradient that facilitates proper lung function.